Electrical heating apparatus for circular ducts

ABSTRACT

An electrical resistance heating apparatus of the type conventionally employed in a rectangular duct is adapted for use in a curved duct by means of an adapter plate attached to the heating apparatus. The adapter plate is curved in shape and complementary to the curvature of the duct. The plate has an opening therethrough in coinciding relation to an opening in the duct and the recessed terminal section and heating coil section of the heating apparatus extend through the plate opening and the duct opening for positioning within the duct with the heater terminal box section of the heating apparatus being positioned outside the duct. The adapter plate is firmly secured to the duct by suitable fasteners when the heating apparatus is inserted into the duct through the duct opening.

United States Patent 1 Brasch et a1.

[ ELECTRICAL HEATING APPARATUS FOR CIRCULAR DUCTS [75] Inventors: Jerome F. Brasch; Rolf G. Albers,

both of Saint Louis, Mo.

[73] Assignee: Brasch Manufacturing Company, St.

Louis, Mo.

22 Filed: Oct. 16,1972

21 Appl. No.: 297,929

ADAPTER PLATE [451 Feb. 26, 1974 3,631,525 12/1971 Brasch 219/375 X FOREIGN PATENTS OR APPLICATIONS 527,817 10/1940 Great Britain 219/318 Primary Examiner-A. Bartis Attorney, Agent, or Firm-Sidney B. Ring; Hyman F. Glass [57] ABSTRACT An electrical resistance heating apparatus of the type conventionally employed in a rectangular duct is adapted for use in a curved duct by means of an adapter plate attached to the heating apparatus. The adapter plate is curved in shape and complementary to the curvature of the duct. The plate has an opening therethrough in coinciding relation to an opening in the duct and the recessed terminal section and heating coil section of the heating apparatus extend through the plate opening and the duct opening for positioning within the duct with the heater terminal box section of the heating apparatus being positioned outside the duct. The adapter plate is firmly secured to the duct by suitable fasteners when the heating apparatus is inserted into the duct through theduct opening.

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Amara PLATE PATENIEB FEB 2 6 I974 sum 2 OF 2 ELECTRICAL HEATING APPARATUS FOR CIRCULAR DUCTS This invention relates to improvements in an electrical heating apparatus and has particular reference to improvements in a resistance wire heater which is installed in and forms part of a forced air heating system.

In recent years forced air heating has become quite popular. Its use has been accelerated by the fact that an air conditioning system can also use the same ducts as the forced air heating system. Furthermore, with the advent of low cost electricity and better engineering and insulation, the use of forced air electric heat has become increasingly popular. The simplicity of the design and use of resistance electric heating units plus the fact that they can be installed economically in a plurality of places in the duct system with individual unit controls has accelerated the trend.

Electrical heating apparatus employed in ducts of forced air heating systems have had their resistance coil terminals positioned in the control box which is installed outside of the air ducts. An electrical heating apparatus of this type is illustrated in U. S. Pat. No. 2,712,588. In certain instances as (1) where the resistance coilterminals are blocked by duct insulation, (2) where the heater has obstructions from components installed in the duct or air handling system, or (3) where the heater is installed in a location having inadequate air flow near the terminal box as, for example, where the heater is mounted close to a bend in the duct work and the control box is located on the inside wall of the bend, etc., the flow of air, which is vital to proper operation, is blocked thus allowing the terminals to build up excessive heat. When this occurs the heater may continually cycle when overheated and eventually cause permanent damage.

U. S. Pat. No. 3,631,525 describes and claims an apparatus capable of avoiding such problems which is characterized by a recessed terminal box (i.e., where the terminal section of the control box is recessed or extended the desired distance into the resistance wire housing unit) which is installed in the duct. As a result, the resistance coil terminals and associated features such as the heat limiters and the automatic reset thermal cutout, etc. are recessed into the air stream of the air duct thus furnishing the terminals with an air flow vital to its proper operation.

In general, conventional heating devices comprise the following:

I. A resistance wire housing unit which containsi 1. the frame housing 2. a series of cross-support attached to the frame housing 1 3. resistance wire heating elements aligned within the housing frame and supported by the cross-supports 4. bushings which insulate resistance wires fromthe cross-supports.

II. The control box which generally contains:

1. resistance wire terminals 2. auxiliary electrical control and supply features which may include some, or all, of the following features, plus others: a. main electrical connections b. fuses c. magnetic contactors d. transformers e. control terminals f. Automatic reset thermal cutout (as a primary safety protection when heater does not have sufficient air flow), etc.

g. manually resettable thermal cutouts or manually replaceable thermal cutouts (heat limiters) as secondary safety projection h. pneumatic electric switches i. fused or non-fused disconnects j. pilot lights k. pilot switches l. automatic or non-automatic circuit breakers m. other features.

Thus, in conventional heaters there are two general housings units:

1. The resistance wire housing unit which when installed fits into the duct. 2. The control box, attached to the resistance wire housing unit, which is installed outside the air duct.

The invention described in US. Pat. No. 3,631,525 in essence contains a true terminal box, (separate and distinct from the control box) containing the resistance wire terminals and related equipment which when installed is positioned within the duct. The remainder of the control box (i.e., which is not recessed into the ducts) is in essence the true control box (as distinguished from a separate terminal box) or a separated terminal section of the control box.

The conventional electrical heating unit sold is rectangular in shape so as to allow it to fit into conventional rectangular ducts. These are generally inserted into rectangular ducts as insert heaters as shown in FIG. 1 of US. Pat. No. 3,631,525.

However, certain heating and/or cooling systems contain circular ducts into which it is difficult or impossible to insert rectangular devices and, if inserted, are extremely insecure.

We have now devised a means for adapting conventional rectangular electrical heating devices to a circular duct which comprises the use of an adapting device. The adapting device is an adapter plate which is firmly attached to both the circular duct and the electrical heating device.

More specifically, the aforedescribed electrical resistance heating apparatus of US. Pat. No. 3,631,525 as herein used and described contains the unitary assembly including l. the heating coil section having positioned and rapported therein the coiled resistance wire heating elements 9 connected to the terminals 10, 10, 10', 10' in the recessed terminal section,

2. the heater terminal box attached to and positioned outside the recessed terminal section, and

3. said recessed terminal section which contains said terminals 10, 10, 10, 10 electrically connected to the controls in said heater terminal box.

Said recessed terminal section is enclosed and attached to and adjacent to said heater terminal box. This electrical resistance heating apparatus including its recessed terminal section and its heater terminal box are so dimensioned with respect to the duct that, when the apparatus is installed, as shown, within and in combination with the duct, as shown, both-the coiled resistance wire heating elements 9 and the recessed terminal section in which the terminals 10, 10, l0, 10' are positioned within the duct, as shown.

The adapting device comprises means for attaching an adapter plate to the electrical heating unit, said plate containing means for attachment to a circular duct when both the plate and the duct have a hole of the proper size through which the heating apparatus may be inserted into the duct. The adapter or attachment plate is joined to the heating unit by means of attaching means, preferably an angular means. The plate is firmly attached to the circular duct, preferably above and below the heating unit. In practice, the attachment or adapter plate is factory or permanently installed.

An embodiment of this invention is shown in FIGS. 1 and 2. FIG. 1 is a sectional view taken on line lll of FIG. 2 showing the heater of this invention inserted into a circular duct. FIG. 2 illustrates diagrammatically a frontal view of the adapter plate and how'it is positioned in the duct.

The adapter plate whose top is l and bottom is 2 is attached to the heater by means of mounting angles 3 and 4 which mounting angles are attached to the heater by any suitable means, such as by means of screws, and attached to the adapter plate by any suitable means, such as by spot welding. The size of the heater and the size and angle of the adapter plate will vary with the duct. The adapter plate herein shown has a shape complimentary to the shape of the duct. Since the duct of this embodiment is circular in shape, the adapter plate is of course arcuate, as shown, in shape Also, as shown, the adapter plate, prior to being placed in its arcuate shape is a substantially rectangular plate. As shown, the openings or holes through which the attaching means,

such as the screws at 7 and 8, are inserted in the adapter plate and the duct and are so positioned that the attachment of the plate to the duct is made at points above and below, respectively, the recessed terminal section and the coil area or heating coil section. In practice, the adapter plate is factory or permanently installed.

A rectangularhole of the proper size is cut in the circular duct and the heater is inserted therein so that points 5 and 6 of the heater touch or are in close proximity (as shown by the dotted lines in FIG. l) to the opposite side of the circular duct. If desired, supporting means may be attached at points 5 and 6 to hold the heater more securely. The entire heating unit is then secured to the circular duct by means of any suitable attaching means such as the screws at 7 and 8. If desired, the openings in the duct into which the heater has been inserted may be sealed by any suiting sealants. The heater is then ready for operation. In practice, the duct installation is done on site.

The essence of this invention is a means of adapting rectangular heating units which are designed for rectangular ducts to be employed as effectively in circular ducts. This is achieved by the present invention.

While there has been shown and described a particular embodiment of the invention it will be obvious that various changes and modifications may be made without departing from the spirit of the invention, therefore it is intended in the appended claims to cover all changes and modifications as fall within the spirit and scope of the invention.

We claim 1. In a conventional rectangular duct electrical resistance heating apparatus including as a unitary assembly (1) a heating coil section in which are supported coiled resistance wire heating elements, (2) a heater terminal box attached to and positioned outside of the heating coil section, (3) a'recessed terminal section containing terminals, (4) each of said coiled resistance wire heating elements being connected to a pair of said termi-- nals, (5) said recessed terminal section being enclosed and attached to and adjacent to said heater terminal box and to said heating coil section and being positioned between said heating coil section and said heater terminal box, (6) said terminals being connected to controls in said heater terminal box, (7) said heating coil section, said recessed terminal section and said heater terminal box being so dimensioned relative to the duct in which the apparatus is to be installed through an opening in the duct so that when the apparatus is installed through said duct opening within the duct both the heating coil section and the recessed terminal section are recessed within the duct while the heater terminal box is outside the duct,

the improvement comprising, in combination therewith, an adapter plate attached to said apparatus for permitting use of the apparatusin conjunction with a curved duct, said adapter plate having an opening therethrough in coinciding relationship with the duct opening, said recessed terminal section and said heating coil section extending through said opening for positioning through said duct opening within said duct so that said heating coil section and said recessedterminal section including said terminals to which saidcoiled resistance wire heating elements are connected are positionable within said duct and said heater terminal box is positionable outside of said duct, said adapter plate having said opening so positioned therethrough'and in such coinciding relationship with said duct opening so as to enable the sealing thereof with said heating coil'section and said recessed terminal section extending therethrough into said duct for preventing air from flowing out of said duct at said adapter and duct openings, said adapter plate being firmly and fixedly attached to said heating apparatus at portions of said heating apparatus above and below said heating coil section and said recessed terminal section, means for fixedly and firmly attaching said adapter plate to said heating apparatus at portions of said heating apparatus above and below said heating coil section and said recessed terminal section, said means being positioned on and attachedto said adapter plate outside of and adjacent to said adapter plate opening, said adapter plate being curved in shape and complementary to said curved duct, whereby said apparatus can be properly installed in a curved duct.

2. The apparatus and improvement of claim 1 wherein said curved adapter plate is arcuately shaped and said duct in which said apparatus is installed is circular in shape. 

1. In a conventional rectangular duct electrical resistance heating apparatus including as a unitary assembly (1) a heating coil section in which are supported coiled resistance wire heating elements, (2) a heater terminal box attached to and positioned outside of the heating coil section, (3) a recessed terminal section containing terminals, (4) each of said coiled resistance wire heating elements being connected to a pair of said terminals, (5) said recessed terminal section being enclosed and attached to and adjacent to said heater terminal box and to said heating coil section and being positioned between said heating coil section and said heater terminal box, (6) said terminals being connected to controls in said heater terminal box, (7) said heating coil section, said recessed terminal section and said heater terminal box being so dimensioned Relative to the duct in which the apparatus is to be installed through an opening in the duct so that when the apparatus is installed through said duct opening within the duct both the heating coil section and the recessed terminal section are recessed within the duct while the heater terminal box is outside the duct, the improvement comprising, in combination therewith, an adapter plate attached to said apparatus for permitting use of the apparatus in conjunction with a curved duct, said adapter plate having an opening therethrough in coinciding relationship with the duct opening, said recessed terminal section and said heating coil section extending through said opening for positioning through said duct opening within said duct so that said heating coil section and said recessed terminal section including said terminals to which said coiled resistance wire heating elements are connected are positionable within said duct and said heater terminal box is positionable outside of said duct, said adapter plate having said opening so positioned therethrough and in such coinciding relationship with said duct opening so as to enable the sealing thereof with said heating coil section and said recessed terminal section extending therethrough into said duct for preventing air from flowing out of said duct at said adapter and duct openings, said adapter plate being firmly and fixedly attached to said heating apparatus at portions of said heating apparatus above and below said heating coil section and said recessed terminal section, means for fixedly and firmly attaching said adapter plate to said heating apparatus at portions of said heating apparatus above and below said heating coil section and said recessed terminal section, said means being positioned on and attached to said adapter plate outside of and adjacent to said adapter plate opening, said adapter plate being curved in shape and complementary to said curved duct, whereby said apparatus can be properly installed in a curved duct.
 2. The apparatus and improvement of claim 1 wherein said curved adapter plate is arcuately shaped and said duct in which said apparatus is installed is circular in shape. 